the board, and each set of pieces is positioned so as to straddle this line. The king and queen start on the innermost ring, with, as is the case in square chess, the queen on a square of the same colour; the bishops start in the second ring from the centre, the knights on the third and the rooks on the outermost ring. The pawns are positioned in front of the pieces. The moves of the pieces are identical to those in orthodox chess; a queen or rook may, if it is not obstructed, move any distance round a ring, except that the "null move" of moving a piece all the way round the board and back to its original square is not permitted. A pawn is promoted after moving six squares from its initial position, to the square immediately before the opponent's starting line. Castling and en passant captures are not permitted. Announcing a check is not obligatory, and "snaffling" (winning the game immediately by capturing the opponent's king after he either moved into or failed to move out of check) is allowed – and has on more than one occasion decided a world championship game. Theory Orthodox chess generally assigns the pieces relative values of 9 points for a queen, 5 for a rook, 3 for a bishop or knight, and 1 for a pawn; although no attempt has been made to assign specific values for circular chess, it is certain that the same values do not hold. The values of the queen and rook are considerably augmented by their greater range – with two rooks or a queen and rook unobstructed on the same ring being especially powerful – while those of the bishop and knight are diminished; for example, on an 8×8 board two minor pieces are held to be stronger than one rook, but on a circular board the rook is considerably stronger. This can be easily seen by just counting the number of squares an unobstructed piece is able to attack on an orthodox and a circular board: the queen, rook, bishop, and knight can attack 27, 14, 13, and 8 squares respectively on an orthodox board, while on a circular board the counts are instead 24, 18, 6, and 6. The minor pieces can, however, pose a significant danger value, as their moves are more difficult to visualise on the circular board and